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G. SMITH, Jr. DIFFERENTIALIULLBY. 'No. 293.281. Patented Feb; 12, 1884.

m Pans. mow, wank-I i 50 wear upon the line.

UNITED STATES PATENT DEEIcE.

GEonGE SMITH, JH, on NEW YORK, Y., AssIGNoR OF ONE-FOURTH To LEANDER THOR-N AND JAMES H; LANGDON, BOTH o SAME PLACE.

DIFFERENTIAL PULLEY.

SPECIFICATION forming- Zo aZZ whom it may concern:

"Be it known that I, GEORGE SMITH, Jr., of New York city, county of New York, and'State ofiNew York, have invented certain new and useful Improvements in Differential Pulleys,

of which the following is'a full, clear, and exact description, reference being had to the accompanying drawings, and to the letters of reference marked thereon.

'My invention has relation to that class of pulleys or pulley-blocks commonly known as differential pulleys; and the object of my said invention is to produce a simple, durable, cheap, and efficient pulley of the class named, wherein the load will be held at any point without danger of slipping, the continuous'rope or line wound and unwound without wearing or abrading one portion against the other, and without unnecessary friction, and on which the rope or line may be quickly and easily replaced by a new one, whenever desired. To accomplish all of this my improvements involve certain novel and useful peculiarities of construction, relative arrange- I ments or combinations of parts, and principles of operation, all of which will be'herein first ,4 fully described, and then pointed out in the claims.

The mere winding and unwinding of a line or chain simultaneously, but with varying rapidity, in order to produce the differential resultant movement, is a principle well 1111- come worn, so that it is impossible to substitute a new chain in the old block or adapt a new block to receive the old chain, in consequence of which the entire device becomesuseless as soon as one of its parts is worn or broken.

been employed, (in this class,) when one part of it reaches the margin of the sheave it ridesup upon the adjacent portion, and practical-t 1y prevents the further hoisting or lowering of the load, besides producing an excessive To obviate this it has ments below explained.

part of Letters Patent No. 293,281, dated February 12, 1884. Application filed September 18,1883. (No model.)

been proposed to employ separate and independent lines, and also to lead the lines about the two sheaves, so.that parts thereof cross tions to the differential-pulley block, as here:

tofore constructed, and secure various advantages by the simple construction and arrange- In the accompanying drawings, forming part of this specification, Figure 1 is :a side ele- 6 5 vation of a differential-pulley block arranged for operation in accordance with my inven tion, and involving the principles thereof, the front plate of the upper or main block being omitted. Fig. 2 is a front elevation, and Fig. 3 a central. vertical section, of the apparatus shown in Fig. 1. Fig. at is a sectional view of the upper and lower sheaves of the main block detached from the frame, indicating a varia- Ition in the number of grooves in the sheaves, 7 5

and different ways in which the sheaves may be cast, all within the limits of my invention; and Fig. 5 is a front elevation of these .two

sheaves with the line wound thereon in accordance with my invention.

Fig. 6 is a plan of the axles of the two sheaves in the difler ential block, showing a slight inclination which it is preferred to give them, one with respect parts. and the furrows formed in the sheaves be- A A are the sides of the differentialblock, whichmay be of any material and any size or shape. I These plates sustain the axles of the 0 upper and lower sheaves therein, and are con-' .nected with any ordinary suspending device, 3 as the hook B. \Vhere the rope or flexible line has O O is the upper sheave, and D D the lower sheave, both provided with grooves to accom- 9 5 mod'ate the rope or line, and both having one ley is in operation both sheaves move together. 10o

2 p wager The relative sizes of these two sheaves (each considered as a whole) may vary to any extent desired; but it is important and necessary, in order that the line may run smoothly and properly, that the circumference of the two sections of the two sheaves shall bear the same relative proportions one to the other-that is, as the circumference of section 0 is to the circumference of section 0, so must circumferenceof section D be to circumference of section D.. Vithout this the line would not pay on and off the sheaves in the proper manner. The diameters of the sheave-sections are of course in the same proportions as their circumferences, and these diameters are most conveniently measured by taking the distancev between the centers of the rope-groove at top and bottom of the sheave. The rope or line is wound about the two sheaves so proportioned,'from outside to outside of the pair, never crossing between them. The grooves are to keep the moving portions of the rope free and clear of each other, and it should be observed that there must be one more groove (in which the rope moves) in each of the sections of the upper sheave than in the corresponding sections of the lower sheave. This is necessary in order that the rope may lead properly. Of these grooves there may be two in each of the lower sections and three in each of the upper sections; or these numbers may be correspondingly increased to any desired extent, though they cannot be decreased and lead and hold the rope in accordance with my invention. The rope 1 S CO11blDl1OLlS bh2tl3 is, after being properly located in the pulleyblock and in the fall, its ends are spliced, and it may be of any length so as to insure the proper travel of the fall upon which the load is applied. It should also be observed that it is immaterial upon which section of the rope the fall is applied, inasmuch as both portions are made to move in equal degrees, though, for convenience, I call one part the hand portion'and the other the fall portion.

E represents the rope, and F the fall, which may be of any character. The rope is wound as follows: Starting from any pointas, for instance, the bottom of the loop in the hand portion, Figs. 2 and 3it is carried up over the outside groove in section 0, down under the outside groove in section D, up over second groove in 0, down under second groove in D, up over third groove in 0, down under third groove in D, up over fourth groove in 0, down behind to the fall, up under the fallpulley, over first groove (at the right) in 0, down under first in D, up over second in 0, down under second in D, up over third in 0, down under third in D, up over fourth in C, then down behind,-;to the starting-point, where. it is spliced. The same system of winding is followed in the case where the lower sheave has only two grooves in each section thereof, and

the upper three, as indicated in Figs. 4. and 5,

- and it is also followed, however the number of grooves may be varied. Being so arranged, when one part of the hand portion is pulled down the fall is compelled to rise, but with a different velocity, depending upon the variations between .the diameters of the two sections of the upper sheave, upon principles well understood. By pulling down upon the other portion the fall will descend,with like difference in velocity. The greater the number of grooves in the sheaves, the greater will be the certainty with which the load maybe held (without slipping) after being elevated. The lower sheave is only employed as a guide for the rope, and the rope must lead from one sheave to the other in a slightly-inclined direction, as best indicated in Fig. 5. To obviate any cramping tendency which might result from this inclination, I locate the axes of the sheaves so that they cross each other, substantially as indicated in Fig. 6. These axes are (supposing the pulley to be suspended freely) in separate planes, and their relative inclinations are very slight, as indicated.

When the pulley is in use, one portion of the hand-rope runs up loosely to its groove in the upper sheave, and would be liable to buckle thereon, or not lead fairly thereto, unless provided with a suitable. guide. To supply this I employ a pair of light rollers, a a, mounted upon the frame of the pulley-block in any light springs, as b b, the tension of which may be adj usted by suitable screws, 0. These rollers insure the proper leading of the rope, by pressing thereon with only sufficient power to keep the rope taut and in proper line, but not hard enough to produce any appreciable resistance to the workings of the pulley.

The sheaves may be of cast metal, and hollow or solid, as may be desired. One made hollow is shown in Fig. 5. They may be cast with the grooves in them, and have only to becleaned out to be made ready for application. The construction is found in practice to be simple and well calculated to answer the several purposes and objects of the invention, as previously set forth. If the rope becomes worn, it has only to be replaced by another, which IOC maybe quickly and easily done, or, if broken,

it may be spliced-advantages which will be readily appreciated. The use of the rope has many advantages over the chain, notably its cheapness, lightness, greater flexibility, and greater ease and smoothness of operating and of handling.

Having now fully described my invention,

what I claim as new, and desire to secure by Letters Patent, is'

1-. In a differential pulley of the character herein set forth, the upper and lower sheaves, grooved for the reception of the rope, each sheave being composed of two sections "movable together, the sections in the two sheaves hear ing the same relative proportions to each other, substantially as shown and described.

2. In a differential pulley, the combination, with the two grooved sheaves, proportioned as explained, and the fall, of the operating-rope wound overand under the larger sections of the two sheaves from outside to.outside, under the fall, and over and under the smaller sections of the two sheaves from outside to outside, and spliced, substantially as shown and described.

3. In a differential pulley having the two grooved sheaves, proportioned as explained, the rope wound thereon, as explained, and the fall,.and the spring-actuated rollers mounted up on the frame of the pulley-block, and serving to guide the hand portions of the rope, substantially as set forth.

4. In a differential pulley, the upper and 15 lower sheaves, grooved for the receptionv of the rope, the axes of the two sheaves being inclined with respect to each other, substantially as shown and described.

In testimony that I claim the foregoing I 20 have hereunto set my handin the presence of two witnesses.

GEORGE SMITH, JR.

Witnesses:

A. BATTGER, W. H. WOODHULL. 

